It failed to drain. Having mannually emptied, it appeared to drain but then wouldn't fill.
The pump does appear to be working now.
We have checked as you suggest but there is nothing obviously disconnected and the appliance is regularly checked for fat. Residual water in the sump is clean.
Can you describe what you mean by the pump impeller please?
Might it be that with switching on and off and manually emptying that we have confused the electronic brain?
Yep, the impeller is in the cover that comes off. That is spinning OK and the surrounding filter is clean. There is some clean residual water in the sump beneath.
There is a small plastic flap at the front of the sump and this seems to be free. I have tried switching on to check but the timer remains on '1' and so it cannot result until '0' until the residual water is gone, I suspect.
I have been inside and with a mirror managed to see that what I thought by touch was a flap was in fact a small piece of glass. We have now managed to remove this, the timer has reduced to zero and we now have an inflow on a test rinse.